I don't understand the buttons, what do they mean? I see a happy face and flower/lamp (?). I think their background should be white when night mode is disabled, they look a bit out of place; the chat too. Edit: I noticed they turn full white after being clicked, I still don't know what they mean, are they just a different icon for upvote and downvote? Edit 2: I found a post explaining it. I think this should be more clear, maybe explained in a tour after registering, because they are a little confusing for someone coming from reddit and they provide no help when you mouse over them.

I would like to know another thing about voting. There are "insightful" and "funny" vote buttons, but on reddit many times I give courtesy upvotes when the other user is trying to be helpful or nice. How should I vote on those things here? What button should I use? Would it be possible to add a "thanks" button?

It's up to you. I'd say vote insightful if they're being helpful. The way it's ranked is insightful is +2 points and funny is +1, but soon we'll enable separate sorting (to see the funniest comments and posts). So if someone is being helpful, just give them a light bulb :). You can even vote both if you want.